1. Field of the Invention
This invention relates to a preferably prefabricated, pre-cut, shaped, milled and profiled structural block that is preferably universally compatible with all existing and preferably all future I-joist manufactured products. The preferred design of the invented support block generally conforms to the side profile of an I-joist, providing added support, reinforcement, nailing surface, bearing area, and protection of the integrity of the I-joist. It may be used at load-bearing points where additional support is required, and/or at joist ends where an increased end-surface area is needed to: a) comply with code specified nailing schedules for attaching I-joists to plates; or b) secure rim boards and trim components to I-joists. This invention may be one component in a continuing, expandable series of products that comprise an I-joist enhancement system, to be used in frame construction projects utilizing I-joists.
2. Description of the Related Art
Several large companies throughout the U.S. manufacture I-joist floor joists and roof rafters for use in frame building construction. According to manufacturers, the advantages of such joists include: a) lightweight for ease of handling, b) product uniformity and consistency, c) availability of long lengths, d) high structural integrity, e) economically competitive, and f) the conservation of old-growth forests through use of composite wood fiber materials.
I-joists are comprised of top and bottom flanges made of solid wood, laminated veneer lumber (LVL) or Oriented Stand Lumber (OSL) with a thin center web between the flanges made of plywood or oriented strand board (OSB) or other structurally approved materials. While these products are well engineered for uniformly distributed top load conditions, the thin web creates unique challenges for concentrated point loads and end-nailing. I-joist manufacturers publish details for conventional vertical solid wood “squash blocks” to be used on either side of joists for additional support. However, there is an absence of specific nailing instructions and details for securing these blocks. Many of these solid wood blocks tend to split at the ends when nailed. Also, potential exists for field error in cutting these blocks square and to correct length. Error can render the blocks useless. Further, there is potential for damage to the structural integrity of I-joists if squash blocks are improperly nailed to the flanges. Most manufactures allow only one (1)16d box nail sideways into the flange every 4″ to 6″ of flange length, thus making it difficult to position and adequately secure squash blocks to opposite sides of an I-joist. Additionally, sideways nailing into the flange is prohibited, in most instances, within 3″ to 4″ from the end of an I-joist. This makes block installation difficult near the perimeter rim board. Incorrect nailing can result in serious structural damage that can result in diminished performance or failure of the I-joist.
Another potential for improper nailing occurs where the end of an I-joist bears on a plate. Code-approved nailing schedules often require a minimum of three (3)8d box nails to secure a joist to a plate. This is impossible when I-joists connect to a standard rim board on a 2×4 plate, and difficult when the I-joists connect to a rim board on a 2×6 plate. Most manufacturers require the first nail be at least 1½″ from the end of the joist. The second nail is usually offset at least ½″ from the first nail or 2″ min. away from the end of the joist on the opposite side of the web. The third nail must be at least 2″ away from the first nail, thus locating it 3½″ to 5¼″ (min.) from the outside edge of the plate, depending on thickness of the rim board and any set-back for sub-siding and/or wall shear panels. This third nail completely misses a 2×4 plate, and potentially only penetrates a 2×6 plate on its very edge.
Therefore, a need exists for a versatile product that provides structural enhancements to the thin web of an I-joist, additional bearing support where required, and improved nailing capabilities.